Homebrew PCBs

johnman9146 wrote:

>That kind of misses the point.  I am looking to see if anyone knows 
>of a suitable etch resist ink, and/or a suitable soldermask ink.
>
>If I do decide to go your way and do the transparancy method with UV 
>sensitive photoresist, I have a few questions.
>
>How do I know when I have the proper exposure?
>
>Can you over-expose?  
>
>How dark black does the transparancy need to be for this method to be 
>effective?
>
>I have access to some pretty sophisticated hardware if I do decide to 
>try this method.  Items such as a photoplotter, a vacuum backed UV 
>table (for exposing printing plates) and more, but it is a hassle to 
>go there for all the neat toys.
>
>I don't think there would be any issues with the image size not being 
>exactly 100% as it is a professional photoplotter designed to make 
>printing plates for magazine reproduction.
>
>Potentially, I may just have to experiment with different inks if 
>nobody has any suggestions.  
>
>Does anyone print legends on thier prototype boards?  
>
>Does anyone use anything to add a soldermask?  
>
>Does anyone even use any type of conformal coating?
>

How much knowledge to you have on ink formulations ? Its an entire field 
of expertise. Inkjet ink chemists are specialized people. You want to 
develop your own inkjet ink that gives high image quality AND can also 
forms a stable acid etch resist ? !  My best bet would search 
http://www.uspto.gov and see if anyone else has done it.  

The reason why everyone uses photoresists is because it works the best. 
 The phototool  is important, and I've only ever seen good ones from an 
inkjet./transparency, I've also seen many more bad ones from various 
inkjets and inkjet transparencies. Its important that the ink and 
transparency are compatible with each other, otherwise you get pin 
holes, banding and rough edges. The Epson stylus series do very good job 
with their dye based black inks on their transparency. Only problem they 
are expensive. I suspect Epson have patented their transparency because 
no one else make one the same. You can print on it then dunk it in water 
and nothing happens to the ink. There are other transparencies that work 
well with the Epson black ink. The HP inkjets use a pigment black and do 
not go so well on Epson transparencies. Use HP transparencies with HP 
ink, the results are quite ok.